1. Field of the Invention
The invention relates to apparatus for performing minimally invasive surgery. More particularly, the invention relates to a retractor instrument suitable for use in endoscopic/laparoscopic surgery.
2. State of the Art
In many surgical procedures it is necessary to retract or pull up on internal tissue structures to create space and to gain access to the operative site. In minimally invasive surgeries this is a particularly challenging task because of the limitations posed by the small incision. Small incisions are made with trocars inside trocar tubes which puncture the body wall. The trocars are removed from the tubes and the tubes are left in place to provide ports to the interior of the body. The diameter of trocar tubes is in the range of 5-20 mm. Generally, the structures that need to be retracted within the body are large and require considerable force to move and keep away from the workspace. Such structures are not likely to fit through the narrow opening provided by a trocar tube.
U.S. Pat. No. 5,514,157 issued May 7, 1996 to Nicholas et al. discloses a plurality of articulating endoscopic surgical tools including a retractor. The retractor consists of three layered blades which can be opened like a fan and then angled relative to the shaft of the instrument. The apparatus utilizes two separate rods to operate the retractor. One rod is pulled back to spread the blades and the other rod is pushed forward to angle the blades relative to the axis of the instrument. The first rod must be flexible to bend as much as the retractor is angled. Thus, the first rod may be subject to breaking or kinking. The second rod is movable from one cam locked position to a second cam locked position. Thus, the angling of the retractor is limited to two positions, zero and forty-five degrees. The three blades can be spread to span a distance approximately three times the diameter of the shaft of the apparatus. However, when spread, the blades form spaces between each other. In other words, the spread blades do not form a unitary surface but three small surfaces with spaces between them.